Display a linear combination: Difference between revisions

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=={{header|REXX}}==

<lang rexx>/*REXX program displays a finite liner combination in an infinite vector basis. */

@.=.; @.1 = '1, 2, 3'

@.=.; @.1 = ' 1, 2, 3 '

@.2 = '0, 1, 2, 3'

@.2 = ' 0, 1, 2, 3 '

@.3 = '1, 0, 3, 4'

@.3 = ' 1, 0, 3, 4 '

@.4 = '1, 2, 0'

@.4 = ' 1, 2, 0 '

@.5 = '0, 0, 0'

@.5 = ' 0, 0, 0 '

@.6 = 0

@.7 = '1, 1, 1'

@.7 = ' 1, 1, 1 '

@.8 = '-1, -1, -1'

@.8 = ' -1, -1, -1 '

@.9 = '-1, -2, 0, -3'

@.9 = ' -1, -2, 0, -3 '

@.10 = -1

do j=1 while @.j\==.; n=0 /*process each vector; zero element cnt*/

do j=1 while @.j\==.; n= 0 /*process each vector; zero element cnt*/

y=space( translate(@.j, ,',') ) /*elide commas and superfluous blanks. */

y= space( translate(@.j, ,',') ) /*elide commas and superfluous blanks. */

$= /*nullify output (liner combination).*/

do k=1 for words(y); #=word(y, k) /* ◄───── process each of the elements.*/

do k=1 for words(y); #= word(y, k) /* ◄───── process each of the elements.*/

if #=0 then iterate; a=abs(# / 1) /*if the value is zero, then ignore it.*/

if #=0 then iterate; a= abs(# / 1) /*if the value is zero, then ignore it.*/

s='+ '; if #<0 then s='- ' /*define the sign: plus(+) or minus(-)*/

s= '+ ' ; if #<0 then s= "- " /*define the sign: plus(+) or minus(-)*/

n=n+1; if n==1 then s=strip(s) /*if the 1st element used, remove plus.*/

n= n + 1; if n==1 then s= strip(s) /*if the 1st element used, remove plus.*/

if a\==1 then s=s || a'*' /*if multiplier is unity, then ignore #*/

if a\==1 then s= s || a'*' /*if multiplier is unity, then ignore #*/

$=$ s'e('k")" /*construct a liner combination element*/

$= $ s'e('k")" /*construct a liner combination element*/

end /*k*/

$=strip( strip($), 'L', "+") /*strip leading plus sign (1st element)*/

$= strip( strip($), 'L', "+") /*strip leading plus sign (1st element)*/

if $=='' then $=0 /*handle special case of no elements. */

if $=='' then $= 0 /*handle special case of no elements. */

say right( space(@.j), 20) ' ──► ' strip($) /*align the output for presentation. */

⚫

end /*j*/ /*stick a fork in it, we're all done. */</lang>

end /*j*/

⚫

/*stick a fork in it, we're all done. */</lang>

⚫

~~'''~~output~~'''~~   when using the default inputs:

<pre>

1, 2, 3 ──► e(1) + 2*e(2) + 3*e(3)